Efficient As(V) removal by NiFe-LDHs and NiFe2O4 in situ growth on 3D porous carbon foam fabricated from waste melamine–formaldehyde foam

The utilization of waste melamine-formaldehyde foam to produce value-added carbon foam has been identified as a promising approach to polymer recycling. Nickel-Iron layered double hydroxides (NiFe-LDHs) and its complex oxides (NiFe 2 O 4 ) were synthesized in this study through a hydrothermal method, growing in situ on the above-mentioned carbon foam substrate. Comparative analysis revealed that CF@NiFe 2 O 4 exhibited superior removal efficiency compared to CF@NiFe-LDHs. Furthermore, arsenate adsorption on CF@NiFe-LDHs and CF@NiFe 2 O 4 conformed more to the pseudo-second-order model; meanwhile, the isothermal adsorption characteristic fitted the Langmuir isothermal model better. The negative ΔG (free energy changes, <-37.68 kJ/mol) and positive ΔH (enthalpy change, 7.64 kJ/mol) indicate that it is spontaneous and endothermic for As(V) to adsorb on CF@NiFe 2 O 4 . Potential mechanisms such as surface complexation, electrostatic interaction, and hydrogen bonding were suggested. This innovative approach offers a novel method for utilizing LDHs-based adsorption materials and recycling waste polymers.